This invention relates to the fabrication of a mold to make an artificial tooth and more particularly to an operator-assisted, computer-controlled method of fabrication of a tooth mold.
Tooth molds are used in the dental industry for the manufacture of artificial teeth. The making of a tooth mold involves an expensive, time-consuming, and laborious process. In addition, the skills of a master craftsman are required and training a person in the art takes approximately two years.
Briefly, the process of fabricating a working mold or a mold used in the routine manufacture of an artificial tooth involves the following steps. A master die of a tooth is used to form a silicone mold. The silicone mold is used to form a working die made of epoxy resin. The above steps are repeated until a desired number of working dies are produced. Multiple working dies are arranged on a template so that eventually multiple copies of a tooth will be made from a single mold. A silicone mold of the dies on the template is prepared and an epoxy mandrel made from the silicone mold. The mandrel is sprayed with silver to acquire an electrical charge and electroplated with nickel to form a coupon which contains escape ways for excess molding fluid and lands or surfaces between furrows on the coupon. The coupon is then mounted on an aluminum frame, mold guide posts are positioned, and a sprue area for entry of the molding fluid is finished on the aluminum frame. The mounted coupon is refined, hand fitted, and hand polished. After inspection, the mounted coupon is referred to as a master mold which is used to make a working mold. It takes approximately 12 to 14 weeks to make the master mold. In addition, the conversion of the positive image from the master die into the negative image of the master mold involves at least five image reversals.
To prepare a working mold which is used in the routine manufacture of an artificial tooth, an epoxy mandrel is made from a master mold. Thereafter, the process of preparing a working mold is quite similar to the process of preparing a master mold after the epoxy mandrel step, that is spraying, electroplating, and refining. The refining steps include the final hand-applied finish-polish step. This process results in a mold of high-definition of the surface properties of the artificial tooth to be produced. It takes approximately six weeks to make a working mold from a master mold.
In practice, two, three, or more different working molds parts, typically three, namely, a face, a shader, and a back mold, are used in the making of a single artificial tooth. The face mold is used for the fabrication of the labial surface of the tooth; a shader mold is used to make the enamel blend of the tooth surface; and a back mold is used for the construction of the back of the tooth.
As can be appreciated from the above outline of the conventional method of tooth mold manufacture, the process is lengthy, costly, and labor intensive. Computer assistance offers a potential means to overcome some of the disadvantages associated with conventional methods of tooth mold manufacture. The prior art automated systems have not been able to generate the high definitional surface patterns necessary for the production of an artificial tooth.
Examples of patents describing automated methods of the manufacture of dental prosthesis and related subject matter include the following. Swinson in U.S. Pat. No. 3,861,044 teaches a method of fitting a tooth with a dental inlay. The method includes the preparation of a tooth for receiving a dental inlay, producing a photographic signal representation of the prepared tooth, transferring the signal representation to an automatic controlled machine tool, filling the prepared tooth area with wax, producing a photographic signal representation of the tooth filled with wax, transferring the signal representation of the tooth filled with wax to an automatic controlled machine tool operating the automatic machine tool under control of the signal representations to produce a dental inlay, and fitting the prepared tooth with the dental inlay.
Heitlinger et al. in U.S. Pat. No. 4,324,546 disclose an apparatus and method for the manufacture of dentures. The patent describes a method useful in the manufacture of dentures in which a prepared tooth stump is reproduced in a working model and a final denture or a temporary replacement piece is suitably conformed to the working model, including the steps of providing electro-optically produced three-dimensional surface information corresponding to the tooth stump, converting the electro-optically produced information corresponding to the tooth stump by a computer into coordinate control signals, and operating a milling machine automatically from the control signals to reproduce the working model of the stump from a block of material.
White in U.S. Pat. No. 4,436,684 describes methods of making three dimension models and mold cavities of internal body structure comprising subjecting the body to radiant energy to produce radiant energy responses internal to the body, detecting the produced radiant energy responses to obtain representations of substances at locations internal to the body defining structures internal to the body three-dimensionally, generating from the representations of the substances a set of three-dimensional coordinates defining a three-dimensional representation of a selected structure internal to the body, and directing a sculpting tool into a workpiece in accordance with the generated set of three-dimensional coordinates to form a model or mold cavity corresponding to the three-dimensional representation of the selected structure.
Moermann et al. in U.S. Pat. No. 4,575,805 disclose a method and a apparatus for the fabrication of custom-shaped implants. A method is described for facilitating the fabrication of a workpiece to be placed onto a light reflective object having a three-dimensional contour to which the workpiece is to be conformed comprising the steps of noncontact topographic scanning of the contour on the object, directing a pattern of reflected light from the object onto a light sensing means, converting the pattern of light on the light sensing means into a corresponding pattern of electrical data, selecting a set of the electrical data, storing the set of the electrical data, mounting the workpiece onto a machining means which is responsive to electrical data sequentially presented, sequentially presenting the stored set of electrical data to the machining means, and machining the workpiece into a three-dimensional shape in accordance with the stored set of data.
Duret et al. in U.S. Pat. No. 4,611,288 describe a system for taking an impression of a body region for the production of a prosthesis comprising a source of nontraumatic light wave energy for generating waves and directing them at a body region to be examined whereby the waves are reflected from the region, a receiver for the waves reflected from the region for generating analog intensity values representing waves reflected from the region, an analog-numerical converter connected to the receiver for transforming the analog intensity values representing the waves reflected from the region into numerical information representing characteristics of the region, means for receiving the numerical information for three-dimensional analysis of the shape and dimensions of the region from the numerical information and for designing a three-dimensional shape corresponding to a finished prosthesis with a contour adapted to fit the region, and signal processing means connected to the means for receiving the numerical information for transforming an output thereof into machine command signals for direct automatic control of a machine for the direct production of a prosthesis by machining of a workpiece to fit precisely to the region.
Moermann et al. in U.S. Pat. No. 4,615,678 teach a blank from which an implant can be machined by an apparatus of the type disclosed in U.S. Pat. No. 4,575,805. The blank is adapted for use in custom fabrication of an implant for dental restoration and includes first and second joined parts. The first part is made of the raw material of the ultimate implant, whereas the second part can be made of a different material. The second part is shaped to facilitate a positive support of the blank in a milling machine, and is preferably equipped with a code-bearing surface which permits information about the physical properties of the blank to be sensed by the machine.
Duret et al. in U.S. Pat. Nos. 4,663,720 and 4,742,464 disclose a method of making a dental prosthesis in which data representing standard tooth shapes and sizes, relationships between teeth and adjacent and occlusive teeth and characteristics for securing a prosthesis to a prepared site, and machining instructions for shaping a blank to the configuration of a dental prosthesis for direct implantation are stored in a computer memory. After preparing a site in the mouth of a patient to receive a dental prosthesis, the dental surgeon optically projects a grating upon the site in the mouth of the patient and generates an interference pattern representing a holistic impression of the site and its relationship to adjacent structures. The interference pattern is converted into data along x, y, z coordinates in a cartesian coordinate system representing machining of a blank to fit the site and matching data obtained by comparing the impression with the computer standards are used to select a best-fit shape and size. A machine tool is numerically controlled with the x, y, z coordinate data and x, y, z coordinate data from the match made by the computer and representing the shape and size of the prosthesis to totally and three-dimensionally fabricate the prosthesis in the machine tool.
Brandestini et al. in U.S. Pat. No. 4,766,704 describe a method and apparatus for machining a custom-shaped dental restorative part from a blank of dental material in a single operation, and include a workpiece being mounted on a support member which facilitates rotation and axial movement of the workpiece. A separating disk is used for almost the entire machining operation, and an additional tool in the shape of a burr can optionally be provided to shape more elaborate pieces. The disk and burr are supported by a tool holder which is supported for movement parallel to and rotationally about an axis. The disk and burr are powered by a closed loop fluid supply arrangement. A tool velocity sensing scheme is utilized for adaptive feed and to compensate for tool wear. The machining mechanism and associated control circuitry are enclosed in a common cabinet so as to provide a mobile unit suitable for use in a dentist's office.
Brandestini et al. in U.S. Pat. No. 4,837,732 teach a method of facilitating acquisition of data defining the three-dimensional shape of prepared teeth and their immediate vicinity comprising the steps of displaying on a video display a live image from a scan head, manually orienting the scan head relative to the prepared teeth while observing the image of the teeth on the video display, thereafter generating from data produced by the scan head in a selected orientation corresponding depth and contrast images, and thereafter processing the depth image based on the contrast image.
These automated methods may be suitable for the preparation of a single prosthesis but the methods reported are not capable of producing the high definitional qualities needed in a mold that will be repeatedly used in the manufacture of artificial teeth. A high-definition mold is required to produce the labial striations or natural markings on a tooth and multiple molds of high definition are needed to produce the necessary blend of color to give a natural appearance to the molded substance of the artificial tooth. However, only the present invention has a computer operator to interact with the system until an acceptable surface pattern model is attained. The present invention is also the only system to use a tool path program to both direct the milling of a mold and direct the finish-polish of the mold. The computer operator interaction and the tool path program-directed finish-polishing, thus, contribute to the making of the high definition mold of the present invention. The prior art teaches the direct production of dental prosthetic parts using program-directed milling and thus teaches away from indirect (computer operator interaction) methods of mold manufacture of dental prosthetic parts.
It is therefore, the primary object of the present invention to provide a method of making a tooth mold possessing the high definitional qualities needed in the manufacture of artificial teeth.
Another object of the present invention is to provide a method of making a tooth mold in a minimum amount of time.
An additional object of the present invention is to provide a method of making a tooth mold that does not require the skills of an artisan.
A further object of the present invention is to provide a method of making a tooth mold that is not labor intensive and, therefore, is less costly than the conventional process.
These and other objects and advantages of the details of fabricating a dental mold will become apparent after reading the following description of the illustrative embodiment with reference to the attached drawing.